Differential signaling circuits can use a pair of complementary signals to transmit data. The pair of signals are generally transmitted using respective electrical conductors. A receiver can decode data carried by the pair of signals by measuring a difference (e.g., a potential difference) between the two signals, instead of measuring a difference between a signal and a reference point (e.g., between the signal's potential and a reference potential or “ground”). Differential signaling circuits can also be used for transmitting differential clock signals.
In an integrated circuit (IC), data and clock signals can be transmitted between different blocks at different locations of the chip using conductive wires (e.g., metal lines and/or vias). To reduce the time delay associated transmitting a signal between two blocks of the chip (e.g., two blocks at opposite ends of the chip), one or more repeaters (e.g., signal buffers and/or inverters) can be inserted into the transmission path, rather than simply inserting a long wire. Each repeater can reproduce its input signal(s) at a higher level (e.g., higher voltage at the output of the repeater than at the input of the repeater), or can restore the input signal(s) to a nominal level. In this way, the repeaters divide the transmission path into several segments of shorter wires separated by repeaters, which together can have a shorter total time delay than the time delay associated with the long wire.
When a signal is transmitted over a medium (e.g., conductive wires) from a transmitter to a receiver, sources of distortion (e.g., signal interference, impedance mismatch, or the medium itself) may cause distortion in the received signal at the receiver. For instance, the received signal can have a different frequency profile from the original signal at the transmitter. As another example, when a pair of differential signals are transmitted over a medium from a transmitter to a receiver, sources of distortion may cause skewing between the two signals, such that the two signals do not switch at the same time (or within a specified time window) at the receiver. Signal equalization techniques are used to prevent, counteract, or reduce the distortion introduced into a signal during its propagation through a medium. For example, de-skewing techniques are used to prevent, counteract, or reduce the skew between the switching times of two or more signals.